Taracus audisioae Shear

Shear, William A. & Warfel, Joseph G., 2016, The harvestman genus Taracus Simon 1879, and the new genus Oskoron (Opiliones: Ischyropsalidoidea: Taracidae), Zootaxa 4180 (1), pp. 1-71: 50-51

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Taracus audisioae Shear

new species

Taracus audisioae Shear   , new species

Figs. 106–115 View FIGURES 106 – 115 , Map 7

Types. Male holotype, male and female paratypes ( CAS) from Meander Cave, Twin Lakes near Burlington Lake, 8620’ asl, Sierra National Forest, Fresno Co., California, collected 2 September 1972 by R. Lem.

Diagnosis. Taracus audisioae   is the largest known species of Taracus   . It is also the only species that consistently shows notable sexual dimorphism in the chelicerae, with males having massive second cheliceral segments and females much more slender ones. The “crassichelis” form of T. pallipes   males is comparable, but in that species the males are dimorphic with the majority having “female-like” chelicerae, and audisioae   males lack the peculiar smooth depression laterally on the second article that is found in crassichelis pallipes   . The penis is of T. audisioae   is long and narrow, with a long aculeus, resembling that of timpanogos   , but notably more slender. Females have fewer abdominal setae, except for pairs of setae along the midline on the first two or three abdominal segments. Unlike any other species, the palpal and first leg coxae do not have setae set on tubercles, nor does the palpal trochanter.

Etymology. This species is named for arachnologist and cave explorer Tracy Audisio of the Okinawa Institute of Science and Technology, who identified and recognized this species as new.

Description. Male from Meander Cave: Total length, 6.67 mm. Carapace medium to dark brown, margins well-defined but color fading laterally to almost white; strongly domed; midline sulcus margined black, extends from anterior margin to ocularium, distinct fovea at about half-length, flanked on each side by pair of setae. Ocularium as wide as long, rounded, relatively low, with four small setae above each eye; eyes large, reflective, narrowly ringed with black pigment. Metapelitidium sclerotized, especially anteriorly, with 3–4 setae on each side of long sensory cone; sensory cone white, tipped brown, acute, tightly appressed to posterior margin of carapace but not set in a recess. Abdomen soft, white or pale tan base color, very slight evidence of sclerotization (detectable change in texture) medial on first two segments, otherwise unsclerotized; dorsum with few setae in scattered groups indicating segments, 4–7 on each side of each ( Figs. 110–111 View FIGURES 106 – 115 ). Ventrally, coxae pale yellowish tan, shaded brown anteriorly and posteriorly. Palpal and leg coxae with numerous stout setae, but these not on tubercles. Thoracic sternum small, arcuate, few setae set in unsclerotized cuticle posterior to sternum. Genital operculum apically rounded, heavily setose, light brown, unspotted, with sclerotized distal lip. Abdominal sternites indicated by sulci between them, with scattered setae.

Chelicerae ( Figs. 114, 115 View FIGURES 106 – 115 ) 18.74 mm long, black. Basal article 6.27 mm long, 0.73 mm wide (L/W = 8.59); second article 8.00 mm long, 2.00 mm wide (L/W = 4.0). Basal article with prominent mediobasal knob, only with numerous seta-tipped tubercles in basal third, ventral row of tubercles extends to tip of article, single row of tubercles dorsally; second article with very numerous prominent tubercles densely arrayed, tubercles more widely spaced and smaller distally. Fixed and movable fingers unusually large, with paired, articulating triangular teeth, narrow, acute tips of fingers cross each other at rest.

Palpi ( Fig. 107 View FIGURES 106 – 115 ) white, shaded light brown distally, total length 18.74 mm, relatively slender; trochanter without prominent, seta-tipped tubercles, femur with regularly spaced slender setae, not set on tubercles. Patella not swollen. Lengths of articles as given in Table 18 View TABLE 18 . Legs long, relatively stout; yellowish tan, unspotted, first two pairs shaded light brown distally. Autospasy sutures of femora undetectable on all legs. False articulations absent from all leg segments. Total lengths in mm of legs 1–4: 21.19, 33.07, 21.00, 26.46. Measurements of leg articles given in Table 18 View TABLE 18 .

Penis ( Figs. 108, 109 View FIGURES 106 – 115 ) 3.16 mm long, 0.21 mm wide (L/W = 15.05), sides of shaft straight, tapering evenly into glans, few small setae subtend aculeus. Aculeus appearing articulated to glans (movable?), basally thin-laminate, tapering to very fine, hair-like tip, pore located at about half-length.

Female from Meander Cave: Total length, 8.08 mm. Descriptive characters of carapace, abdomen and ventral surface as in male.

Chelicerae ( Figs. 112, 113 View FIGURES 106 – 115 ) 13.31 mm long, basal article 6.31 mm long, 0.69 mm wide (L/W = 9.14); second article 7.00 mm long, 1.00 mm wide (L/W = 7.0). Total length of palpus ( Fig. 106 View FIGURES 106 – 115 ), 18.18 mm; palpal trochanter without seta-bearing tubercles. Total lengths in mm of legs 1–4: 19.57, 31.57, 19.58, 25.41; lengths of leg and palpal articles as given in Table 19 View TABLE 19 . Second leg metatarsus with 12 faint false articulations, none in other legs. Ovipositor typical. Other appendage characters as in male.

Distribution. All records CAS. CALIFORNIA: Fresno Co.: Meander Cave, Twin Lakes near Burlington Lake, 8620’ asl, Sierra National Forest, 2 September 1972, R. Lem, Ƌ ♀♀; 20 June 1970, T. Briggs, Ƌ ♀; Hidden Pond Cave, near Huntington Lake, 8620’ asl, 2 September 1972, T. Briggs, ♀. Mono Co.: Mill Creek, 10,700’ asl, 14 August 1972, T. Briggs, Ƌ. Tulare Co.: White Chief Cave, 3 miles south of Mineral King post office, 14 September 1968, T. Briggs, ♀; Cirque Cave, 3 mi south of Mineral King, 11,000’ asl, 15 September 1968, ♀♀; Panorama Cave, 22 July 2004, J. Krejca, C. Walck, S. Fryer, ♀. Tolumne Co.: Forsythe Cave, 18 July 2004, J. Krejca, C. Walck, S. Fryer, ƋƋ ♀♀.

Most of the records are from Kings Canyon Sequoia National Park. The Mono County record is the only surface collection, but it is likely that the species has other surface-dwelling populations; collecting in the parks has been focused on caves.

Notes. In Cirque Cave, T. audisioae   is syntopic with the much smaller Oskoron spinosus   .

TABLE 18. Lengths in mm of palpal and leg articles of male Taracus audisioae.

  Femur Patella Tibia Metatarsus Tarsus
Palpus 7.70 4.21 5.16 - 1.67
Leg 1 6.13 1.53 3.53 6.33 3.67
Leg 2 8.00 1.67 6.67 9.73 7.00
Leg 3 5.07 1.40 3.53 6.47 4.53
Leg 4 6.67 1.53 4.80 8.13 5.33

TABLE 19. Lengths in mm of palpal and leg articles of female Taracus audisioae.

  Femur Patella Tibia Metatarsus Tarsus
Palpus 7.49 4.13 4.97 - 1.59
Leg 1 5.36 1.43 3.14 5.93 3.71
Leg 2 7.36 1.71 6,64 9.42 6.43
Leg 3 5.36 1.29 3.29 5.71 3.93
Leg 4 5.93 1.43 4.64 7.43 5.71

California Academy of Sciences